Produce That Benefits Most from Hydrocooling

Proper cooling is essential for almost any type of produce in order to ensure that quality is preserved as fruits and vegetables begin their journey to the end consumer. Here at SEMCO/SEMCOLD LLC, we offer many different kinds of cooling systems and different cooling methods are better suited to different types of produce. In this article let’s take a look at hydrocooling and the produce that benefits most from this method.

Hydrocooling-Produce

Why Produce Cooling Is So Important

Good produce cooling is important for a number of reasons. Field heat, or the ambient temperature that permeates a plant while it is growing, can have many detrimental effects that begin to affect the produce as soon as it is harvested. These include wilting due to water loss, rapid cellular respiration that leads to softening, and high levels of ethylene production, which can make the fruit overripe. In addition, warmer temperatures are more hospitable to decay-causing microorganisms such as molds and bacteria.

Proper cooling as soon as the crop is picked can slow, delay, or even prevent many of these undesirable processes. It is important to ensure that field heat is rapidly dissipated as soon as possible after the produce has been harvested. This keeps fruits and vegetables fresher for longer, decreasing the urgency to sell and improving overall quality once it is purchased.

Hydrocooling Basics

Hydrocooling is a cooling method in which produce is directly cooled by chilled, near-freezing water. This cold water runs over the fruits and vegetables, quickly dropping their temperature and eliminating problems due to heat. The water is cooled either with ice, a refrigeration system, or a system specially designed for hydrocooling.

The Advantages of Hydrocooling

There are many benefits to hydrocooling. One of the biggest is that it is very rapid; water transfers heat away from food up to 15 times more rapidly than air does. Hydrocooling systems can be designed for a range of operation sizes, capable of handling both small loads and very large ones. Also, hydrocooling helps prevent moisture loss in produce, ensuring that the fruits and vegetables will not dry out—a common concern with some other types of cooling systems.

In addition, depending on the design of the system, hydrocooling can also act as a way to partially wash the produce. This is not true, however, for hydrocooling systems where the water is recirculated without being purified. These are a few of the reasons why hydrocooling is a popular option among produce growers.









Important Considerations for Hydrocooling

A number of factors should be taken into account when trying to decide if hydrocooling is the best option for a crop. One of the biggest is concern about rot and disease. Although colder temperatures discourage decay, wet environments are friendly to microorganisms, meaning that some of the disease-prevention benefits of cooling can be reduced. For many types of produce, this difference is negligible, but foods that are especially susceptible to disease should not be hydrocooled.

In addition, the type of packaging should also be considered. Hydrocooling should be avoided for packages that are not water permeable, preventing the water from flowing inside and around the produce. Also, the packages must be designed to drain well, so that the water does not collect and pool in the storage area. Mesh bags, bulk bins, and wire crates are well-suited for hydrocooling; palletized produce can be hydrocooled if it is stacked correctly.

Finally, it is important to note that hydrocooling is primarily a pre-cooling method meant to remove field heat rapidly. Hydrocooling is not advisable as a standalone cooling method because at lower temperature it is not energy efficient. Hydrocooling is often done in conjunction with room cooling or forced-air cooling.

Best Produce for Hydrocooling

There are many types of fruits and vegetables that respond particularly well to hydrocooling. These include:

  • Apricots
  • Peaches
  • Plums
  • Nectarines
  • Cantaloupe
  • Apples
  • Pears
  • Cherries
  • Spinach
  • Lettuce
  • Endive and other greens
  • Leeks and Green Onions
  • Asparagus
  • Broccoli
  • Snap Beans
  • Pea Pods
  • Brussel Sprouts
  • Cauliflower
  • Turnips
  • Cucumbers
  • Corn

Foods that should not be hydrocooled include those that are highly susceptible to wetting, such as berries, potatoes, bulb onions, and garlic. This type of cooling should also be avoided for citrus fruits, mushrooms, grapes, and squash. For information regarding cooling methods for particular types of produce be sure to check out our past articles.

SEMCO/SEMCOLD LLC Designs Great Hydrocooling Systems

Here at SEMCO/SEMCOLD LLC, we are proud to offer a wide variety of cooling solutions to our clients with our specialty design, manufacture, and installation services. Hydrocooling is just one excellent option for keeping your produce fresh and your quality high. Contact us for more information regarding the system that is best for your crop.

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Methods for Cooling Blueberries After Harvest

Research has shown that blueberries tend to be an impulse buy for most consumers rather than a planned purchase. For this reason it is imperative that the blueberries which eventually make it to grocery stores be fresh, high quality, and visually appealing. In order to accomplish this goal the blueberries must be well cared for from planting, growth, and harvest, right on through to cooling, storage, transport, and display. The cooling and storage segment is especially important because it is during this crucial phase when the blueberries will either shrivel, rot, and decay or maintain their quality and thrive.

General Facts About Blueberries

Blueberries are commonly classified as either highbush or lowbush, with the term highbush referring to larger varieties of cultivated blueberries, including the vast majority of those commercially sold, and the term lowbush referring to smaller, wild varieties of blueberries, which are not as commonly sold. Blueberries are an early summer fruit and are highly perishable with a relatively short shelf life compared to many other types of fruits of vegetables. Depending on the weather and other conditions a blueberry field may be harvested as many as four times during the season, typically in intervals of about five to seven days. If the fields are harvested less often the result is typically over-ripe blueberries which are not as suitable for transport and sale, while harvesting more often is typically an inefficient use of labor and resources.

Blueberries are very susceptible to physical damage from careless or rough handling, picking, or mechanical harvesting. They should thus be handled very carefully and it is imperative that they be cooled rapidly and efficiently to preserve quality and extend shelf life. A successful cooling and storage system for blueberries is paramount.

General Information About Cooling and Storing Blueberries

If blueberries are allowed to remain at field harvest temperatures they are extremely perishable and will being to decline in quality very quickly. Visible signs of decay may be evident in warm, wet blueberries as soon as 12 hours or less after they have been harvested. For this reason they should never be held all day without proper cooling and storage. They should also not be picked while wet, such as immediately after or during a rainstorm, because wet blueberries are more susceptible to postharvest decay organisms such as the ones that cause gray mold and Alternaria rot. As a general rule of thumb blueberries should never go more than four hours without being cooled, but should be cooled sooner still if possible.

Respiration – Like other fruits blueberries are alive at the time of harvesting and continue to respire even after they have been picked. There is a natural rise in temperature due to this continued respiration. It has been estimated that blueberries generate about 22,000 Btu of heat per day per ton due to respiration. This is enough to raise their temperature by as much as 6°F. If that extra heat is not removed by cooling it will hasten the ripening and decay process.

Proper cooling will dramatically increase shelf life and slow the decay caused by respiration. That is because the respiration rate is directly impacted by the temperature of the blueberries. Blueberries respire at almost 20 times the rate at 80°F compared to 40°F. That means that they have almost 20 times the shelf life as well. The optimum temperature to slow respiration and increase shelf life is about 33°F to 34°F.

Humidity – Blueberries have a high water content and require a high relative humidity to remain moist and flavorful. If there is not adequate humidity in the air this can result in the blueberries becoming dried out and suffering water-related weight loss. The optimum relative humidity for blueberries is between about 90% and 95%.

Freezing – Blueberries will freeze at about 28°F. Freezing is a viable method of extending shelf life, but it must be done intentionally and quickly and the temperature should then be maintained below 0°F. Blueberries may suffer freeze damage if they are unintentionally subjected to temperatures below 28°F and then allowed to warm up again.

Correct Method of Cooling Blueberries

One of the most common cooling methods is called room cooling. In room cooling the product is placed in a refrigerated room and allowed to gradually cool to the ambient temperature. However, this method is not suitable for blueberries because the cooling rate is too slow to prevent continued degradation and quality loss. A large part of the problem is that the containers, wrappers, and plastic needed to hold the blueberries acts a kind of insulation, keeping the heat in. Room cooling not only results in inadequate cooling, but also non-uniform cooling, with some blueberries getting significantly cooler than others.

Forced-Air Cooling – The solution to this problem is forced-air cooling. In forced-air cooling, the blueberries are arranged around fans which then pull cooled air through the berries. This results in a much faster, and more uniform rate of cooling. Depending on the particular circumstances, forced-air cooling is about 16 to 20 times faster for cooling the blueberries than attempting to use still-air room cooling alone. This results in blueberries that have a much longer shelf life and which will reach the end consumer in much better condition.

For businesses that sell blueberries and blueberry products, be they farms, factories, or grocery stores, quality is of the essence. It is the quality of the product around which the business will build and maintain its reputation and keep customers coming back. SEMCO/SEMCOLD LLC can help with this crucial area by supplying industry-leading, efficient, customizable blueberry cooling equipment and systems. Our products and product lines are versatile and can be developed to suit each customer’s unique requirements.

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Methods for Storing and Cooling Onions After Harvest

As we cover methods for cooling onions, they are one of the most widely used food items in the US. They are an important flavoring component in countless dishes and are even eaten raw on sandwiches and salads. Onions are also rich in antioxidants and flavonoids which may bring a number of healthful benefits including anti-cholesterol, anti-inflammatory, and anti-cancer. For onions to properly serve their crucial culinary and nutrition niche, they must be stored, cooled and transported carefully in ways that take the quality and freshness needs of the onion into consideration.

General Facts About Onions

The phrase onions encompasses a wide array of different bulb vegetables in the Allium genus, including such exotic members as the Egyptian onion (A. ×proliferum), The Japanese bunching onion (A. fistulosum), and the Canada onion (A. canadense) to name just a few. However, most varieties of common onions are in the A. cepa species, including red onions, yellow onions, white onions, shallots, and potato onions, each of which has a different and distinct flavor.

Onions pose a unique challenge to growers because unlike many other fruits and vegetables which can go straight from harvest into cooling and storage, onions need to be dried first. In some regions onions are dried in the field; however, areas with high humidity and rainfall during onion harvesting season must instead dry the onions by other means such as in bins and barns, often with carefully regulated humidity and temperature.

General Information About Cooling and Storing Onions

Like other fruits and vegetables onions have specific cooling needs which include factors such as temperature, humidity, handling, and storage. As discussed above onions also require drying. Depending on the resources available some farmers have had success repurposing equipment and facilities used for drying tobacco, peanuts, and other crops into use for drying onions.

Drying – Drying is crucial to reduce the onion’s susceptibility to decay organisms, extend their shelf life, and vulnerability to bruising. Even dried onions are of course still subject to eventual decay and physical damage, but drying helps provide them with extra time and resistance. Drying times will vary from two or three days if heated air is used, to anywhere upwards of one or more weeks if only ambient air is used.

Humidity – During drying onions should be exposed to a relative humidity of about 65%. Higher humidity levels will lengthen drying times or even prevent full drying. This will also increase the onion’s risk of neck rot and other problems. Once the onions are dried and are in cold storage a slightly higher humidity of about 70% to 75% is generally acceptable.

Temperature – During drying heated air temperature should be 100°F. Higher temperatures should be avoided since anything over 110°F can damage the onion. Once the onion is dried it should be stored in a cooler or cool environment with a temperature between 32°F and 36°F. It is important to prevent the temperature from reaching 31°F or lower because his will subject the onion to freeze damage.

Storage – Temperature and humidity greatly impact how long an onion can viably be stored and at what rate the onion loses mass. Onions stored in temperatures 50°F or higher may be subject to sprouting.

Exposure to Other Produce – Onions should also be kept separate from other fruits and vegetables, both to protect the onion and the other food. That is because onions will readily leach moisture from other produce, drying out the other food and exposing the onion to too much moisture for proper storage. Onions also have a very pungent odor and many other types of produce may absorb the smell.

Cooling Method for Onions

Onions should be cooled using the room cooling method. This involves placing them in a refrigerated room or large walk-in cooler. It is important to continue monitoring temperature and humidity levels while the onions are in the cooler.

Long-Term Storage

Onions can also successfully be placed in controlled atmosphere storage for even longer-term storage. This involves carefully regulating not only temperature and humidity levels, but also the onion’s exposure to gases such as oxygen, nitrogen, and carbon dioxide. Onions in controlled atmosphere storage may last up to 8 months with minimal quality loss.

SEMCO/SEMCOLD LLC offers quality cooling equipment that can be customized and designed to fit the needs of onions. We can also tailor our systems to the particular capacity demands and other requirements of our customers. Please contact us for more information.

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